Directions

Combine half the Cheddar and half the Parmesan cheese in a large bowl. Mix together lightly. Knead in 4 tablespoons of mayonnaise until mixture is creamy and very smooth.

Work in remaining cheese, garlic, shallot, pimientos, 1 tablespoon of reserved pimiento liquid, a dash of cayenne and a small pinch of dry mustard. Knead just enough to mix well: it should still have plenty of texture. Add remaining mayonnaise, if necessary—just enough to make it spreadable.